Three scientists from Japan, China and Ireland whose discoveries led to the development of potent new drugs against parasitic diseases such as malaria and elephantiasis won the Nobel Prize for Medicine on Monday.

Irish-born William Campbell and Japan’s Satoshi Omura won half of the prize for discovering avermectin, a derivative of which has been used to treat hundreds of millions of people with river blindness and lymphatic filariasis, or elephantiasis.

China’s Youyou Tu was awarded the other half of the prize for discovering artemisinin, a drug that has slashed malaria deaths and has become the mainstay of fighting the mosquito-borne disease.

Some 3.4 billion people, most of them living in poor countries, are at risk of contracting these parasitic diseases.

“These two discoveries have provided humankind with powerful new means to combat these debilitating diseases that affect hundreds of millions of people annually,” the Nobel Assembly at Sweden’s Karolinska Institute said.

“The consequences in terms of improved human health and reduced suffering are immeasurable.”

Traditional medicine

Today, the medicine ivermectin, a derivative of avermectin made by Merck & Co., is used worldwide to fight roundworm parasites, while artemisinin-based drugs from firms including Sanofi and Novartis are the main weapons against malaria.

Omura and Campbell made their breakthrough in fighting parasitic worms, or helminths, after studying compounds from soil bacteria. That led to the discovery of avermectin, which was then further modified into ivermectin.

The treatment is so successful that river blindness and lymphatic filariasis are now on the verge of being eradicated.

Youyou turned to a traditional Chinese herbal medicine in her hunt for a better malaria treatment, following the declining success of the older drugs chloroquine and quinine. This led to the isolation of artemisinin, a new class of anti-malaria drug.

“We now have drugs that kill these parasites very early in their life cycle,” said Juleen Zierath, chair of the Nobel Committee. “They not only kill these parasites but they stop these infections from spreading.”

Despite rapid progress in controlling malaria in the past decade, the disease still kills around half a million people a year, the vast majority of them babies and young children in the poorest parts of Africa.

The 8 million Swedish crown ($960,000) medicine prize is the first of the Nobel prizes awarded each year. Prizes for achievements in science, literature and peace were first awarded in 1901 in accordance with the will of dynamite inventor and businessman Alfred Nobel.